Interactions between early nutrition and the immune system

The ontogenetic development of the immune system is a well-defined, almost stereotyped event. The anlagen of the human thymus can be distinguished in the third and fourth branchial arches in the sixth week of gestation. Several distinct responses have been observed in the first trimester of fetal development. In addition to genetic factors, environmental influences such as nutrition play an important role in influencing the developing human immune system. Adverse factors that impair fetal growth hinder immunological maturation as well. These include maternal malnutrition, smoking, alcohol and other substance abuse, placental insufficiency and infection. The immunocompetence of low birth weight infants is compromised; those who are small for gestation show persistent immunological impairment for several months, even years. Prolonged effects on immune responses can be seen in animal models of fetal malnutrition. A second area where interactions occur between dietary factors and the immune system is the IgE-mediated allergic response. Those with a family history of atopy are at high risk of developing allergic disease in late childhood and adult life. The enormous costs of atopic disease in terms of health management and physical and emotional isolation have led to attempts at prevention. These strategies include restriction of the mother's diet during pregnancy and lactation to exclude common allergenic foods and prolonged exclusive breast feeding. Casein or whey hydrolysate formulas are advisable in those not breast fed.